1. Field of the Invention
This invention relates to a digital movement data recording apparatus for recording vehicle movement data indicating moving conditions of a vehicle such as speed and travel distance onto an external record medium.
2. Description of the Prior Art
Vehicle movement data recording apparatuses of the type mentioned above are carried on a vehicle for first monitoring the moving state of the vehicle to produce digital movement data indicating moving conditions of the vehicle, and then compressing the above digital movement data in accordance with a predetermined set value so as to finally record the thus compressed digital movement data onto an external record medium. The external record medium is made of an IC (Integrated Circuit) memory card and so forth which can be loaded into and unloaded from the recording apparatus, and the data recorded on the external record medium is read out by an analyzing apparatus installed at an office for the supervision of movements of vehicles from such record medium and expanding and analyzing the thus read digital movement data.
More specifically, the digital movement data recording apparatus comprises a CPU (micro-computer) for sampling and receiving electric signals from a rotation sensor which is connected to a transmission mechanism of the vehicle, by way of a suitable connecting means, and determining an instantaneous speed and a travel distance of the vehicle by calculation in accordance with the thus received electric signals and executing various jobs including compression of data in preparation for recording of the speed data and travel distance obtained by the calculation as digital data onto an external record medium.
The above described vehicle movement data digitally recorded in an external record medium is excellently effective for supervision of the moving state of the vehicle.
However, with the conventional recording apparatus described above, since recording capacity of the external record medium is limited, the recording capacity runs short in accordance with the normal recording operation of the digital movement data, and as a matter of fact there will be an occasion that there is no recording space left in the record medium for recording the movement data and that no further data can be recorded after the point where the recording capacity has run out, with the result that one can not attain the complete recorded data. The same thing can happen when an external record medium with no recording space is loaded into the recording apparatus, in which case there will be absolutely no recorded data left.